You have no way of knowing how long the amalgam of lost ships drifted in the warp before appearing once again in real space. Centuries at least, maybe millennia.

In all of The Imperium, there are few artifacts as prized as a Space Hulk. Such structures nearly always contain a wealth of lost technologies from ages past, yet they're as dangerous as they are valuable. After so many centuries in the warp, Chaos Corruption is inevitable. If anything lives on board this city-sized vessel, you'll be quite fortunate if they only want to kill you.